Device for searching for defects on parts by endoscopy

ABSTRACT

A device for searching for defects on parts that are masked, such as turbine engine blades, the device including a tubular sheath, a light-guide guiding light, an image-transmission mechanism transmitting images housed inside the sheath, an examination head at a distal end of the sheath including an illumination mechanism and an image-taking mechanism connected to the light-guide and to the image-transmission mechanism housed in the sheath, a mechanism spraying a succession of penetrant test materials on the part for inspection including a capillary slidably guided in a duct housed in the sheath, and a mechanism adjusting orientation of the examination head at the distal end of the sheath.

The invention relates to a device for using endoscopy to search fordefects on parts that are masked, i.e. that are not directly visible,e.g. such as parts inside a turbine engine.

It is known to inspect the internal components of equipment or of amachine with the help of an endoscope which is an elongate opticalinstrument of small diameter that is passed through a small orifice in awall in order to examine the appearance of components that are to befound on the other side of the wall. The endoscope can thus be used forinspecting blades of a turbine engine such as an airplane turboprop orturbojet without it being necessary to disassemble the engine.

In order to view defects of a part, it is known to use a penetrant testtechnique that consists in depositing organic materials on the surfaceunder examination of the part and in observing under ultravioletillumination the extent to which the organic materials impregnate thesurface of the part. The presence of defects is revealed after dryingthe surface of the part and depositing a developer material that revealsthe organic material that has infiltrated into surface defects of thepart when the part is illuminated with ultraviolet light.

In order to facilitate the use of the penetrant testing technique on anairplane engine while it is attached under the wing of an airplane,proposals have already been made in document U.S. Pat. No. 4,273,110 touse an endoscope incorporating penetrant test means. For that purpose,the proposed instrument comprises an elongate rigid cylindrical sheathof small diameter containing a duct that is used for passing means forguiding ultraviolet light and visible light towards an end of theinstrument that is close to the part for inspection. The instrument alsohas an optical duct for integrating means for transmitting and formingimages in order to observe the illuminated zone, and a plurality ofducts, each used for passing a respective penetrant test material.

That type of instrument is relatively easy to use when it is desired toexamine a masked part, i.e. a part that is not directly visible and thatis situated behind a wall. For that purpose, it suffices to insert therigid sheath through an orifice in the wall and to perform theinspection in the manner described above. The Applicant has also madeproposals in a prior application FR 2 857 094 to perform the penetranttesting and the observation with the help of two separate endoscopes. Inanother prior application, FR 2 861 185, the Applicant proposes using anendoscope with ultraviolet illumination and deflected distal viewing,the endoscope having a rigid tubular body.

Nevertheless, those prior devices require a plurality of independentducts for passing different penetrant test materials, thereby requiringthe endoscope to have a section that is large and restricting its use toorifices or passages that are sufficiently large.

A particular object of the invention is to provide a solution to thatproblem that is simple, satisfactory, and inexpensive.

To this end, the invention provides a device for searching for defectson parts that are masked and accessible via a passage that is notrectilinear inside a turbine engine such as an airplane turboprop orturbojet, the device comprising a tubular sheath and light-guide meansfor guiding light and image-transmission means for transmitting imageshoused in the sheath in order to illuminate and observe a part forinspection, the device being characterized in that it comprises anexamination head at the distal end of the sheath, the head havingillumination means and image-taking means connected to the light-guidemeans and to the image-transmission means housed in the sheath, meansfor spraying a succession of penetrant test materials on the part forinspection, said means comprising a capillary slidably guided inside aduct housed in the sheath, and in that it includes means for adjustingthe orientation of the examination head at the distal end of the sheath.

Integrating a duct inside the sheath makes it possible to insert andwithdraw a capillary for passing a penetrant test material, whichcapillary is mounted to slide inside the duct, thus making it possibleto use a plurality of capillaries in succession, each capillary beingdedicated to pass one particular penetrant test material. The diameterof the tubular sheath can thus be smaller than the diameter of a priorart sheath.

Slidably inserting the capillary inside the duct also makes it possibleto bring the distal end of the capillary close to the zone of the partwhere it is desired to apply the penetrant test material. In thismanner, the illumination means and the image-taking means may be setback from the distal end of the capillary. This avoids penetrant testmaterial spray from becoming deposited on the illumination means or onthe image-taking means. When the operator desires to observe the treatedregion, the operator pulls on the proximal portion of the capillary inorder to bring its distal end closer to the distal end of the sheath.

According to another characteristic of the invention, the devicecomprises air-blow means for blowing air on the illumination means andimage-taking means located at the distal end of the sheath.

The air-blow means prevent the illumination means and the image-takingmeans from being polluted by the various penetrant test materialsinjected via the dedicated capillaries that are inserted in successioninto the duct.

In a particular embodiment of the air-blow means, they comprise meansfor feeding air under pressure that are connected to a blow tube leadingat its distal end to the vicinity of the illumination means and theimage-taking means.

In a preferred embodiment of the invention, the means for feeding airunder pressure are connected to the proximal end of the duct for passingthe capillary in order to feed the duct with a continuous stream of airthat leaves via its distal end.

In operation, the stream of air that blows continuously between theinside surface of the duct and the capillary prevent drops of penetranttest materials such as acetone, a penetrant dye, an emulsifier, or adeveloper, or indeed washing water, from becoming deposited inside theduct.

According to another characteristic of the invention, the proximal endof the flexible sheath is connected to a handle for fastening to theengine and the duct housing the capillary is extended inside the handleand is connected to a rigid tube carried by the handle and serving toinsert the capillary into the inside of the duct.

According to another characteristic of the invention, the devicecomprises holder means for preventing the capillary from sliding insidethe duct, constituted by an endpiece designed to be engaged and heldagainst the free end of the rigid tube, the endpiece having means forclamping onto the capillary by pinching it.

In a particular embodiment of the invention, the endpiece includes apassage leading to the inside of the tube and forming an inlet forconnection to the means for feeding air under pressure.

In this configuration, the endpiece with the clamping means also servesto make a connection with the means for feeding air under pressure.

According to another characteristic of the invention, the orientationadjustment means comprise a control member for controlling the angularorientation of the examination head, which member is rotatably mountedon the endoscope handle and is connected to transmission means fortransmitting the orientation control to the examination head, thesetransmission means being housed in the sheath.

Turning the control member in one direction or the other serves to causethe examination head to tilt relative to the remainder of the sheath.

In a particular embodiment of the invention, the means for adjusting theorientation of the examination head comprise at least two cables guidedinside the sheath and fastened at their distal ends to the examinationhead at two diametrically opposite points, and wound under tension attheir proximal portions in opposite directions on a rotary controlmember situated on the handle.

In another particular embodiment of the invention, the means fortransmitting the orientation control comprise at least one rod extendinginside the sheath and connected at its distal end to a mechanism forconverting rotary movement of the ring into movement in translation ofthe rod, the rod being connected by its distal end to a finger that ispivotally hinged to the distal end of the sheath about an axis that isperpendicular to the sheath.

Advantageously, the distal finger includes an axial channel for passingthe capillary and is hinged to pivot between a position in which it isin alignment with the axis of the sheath and a position in which it isoriented perpendicularly to the axis of the sheath.

The pivoting of the hinge finger induces pivoting of the distal end ofthe capillary, thereby enabling the distal end of the capillary to beoriented angularly in three dimensions in order to spray the penetranttest materials on the part for inspection.

In a preferred configuration of the invention, the tubular sheath isflexible and the capillary is flexible, thereby making it possible toperform non-destructive inspection of a part that is to be found insidea complex three-dimensional structure and that is accessible solely viaa narrow and non-rectilinear passage, where this is not possible usingan endoscope of rigid structure.

According to another characteristic of the invention, the distal end ofthe sheath is fitted with a spray endpiece at its distal end.

Preferably, the spray endpiece at the distal end of the capillary isremovable and can be selected from a set of spray endpieces for sprayingradially, forwards, or backwards.

In a practical embodiment of the invention, the sheath is of circularsection with a diameter lying in the range 6 millimeters (mm) to 10 mm,and the duct for passing the capillary has a diameter of about 1.2 mm,the capillary having a diameter of about 0.8 mm.

According to another characteristic of the invention, the device hasfastener means for fastening to a portion of the engine, which meanscomprise a hinge arm connected to the handle.

The invention also provides a method of non-destructively inspecting amasked part inside a three-dimensional structure by means of theabove-described device, the method consisting in:

-   -   inserting and guiding the examination head inside a        three-dimensional structure to a position for examining the part        for inspection;    -   with the examination head placed facing the part for inspection,        feeding the proximal end of the capillary with a first penetrant        test material and applying this material via the distal end of        the capillary to the part for inspection;    -   slidably withdrawing the capillary from the duct in which it is        housed; and    -   slidably inserting a second capillary into the duct and bringing        its distal end into the vicinity of the part for inspection, and        then feeding the proximal end of the second capillary with a        second penetrant test material and applying the second material        to the part for inspection.

Other advantages and characteristics of the invention appear on readingthe following description made by way of non-limiting example and withreference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of a prior art device for searching fordefects;

FIG. 2 is a diagrammatic perspective view of a device of the inventionfor searching for defects;

FIG. 3 is a diagrammatic section view of the flexible sheath of thedevice of the invention;

FIG. 4 is a diagrammatic perspective view on a larger scale of theproximal portion of the FIG. 2 device;

FIG. 5 is a diagrammatic end view of an endpiece having inserted thereina capillary for passing a penetrant test material;

FIG. 6 is a diagrammatic view of the distal end of the duct housing acapillary;

FIG. 7 is a diagrammatic view of the penetrant test material beingsprayed;

FIG. 8 a is a diagrammatic section view of the distal end of theflexible sheath of the device of the invention;

FIG. 8 b is a diagrammatic view in section of the distal end of theexamination head of the device of the invention;

FIG. 9 is a perspective view of an orientable examination head of thedevice of the invention;

FIG. 10 is a diagrammatic view of an arm for holding the endoscope ofthe invention;

FIGS. 11 to 13 are perspective views of endoscopic equipment having arigid inspection tube and adapted to penetrant testing under ultravioletillumination in an embodiment of the invention;

FIG. 14 is a perspective view of the distal end of the endoscope ofFIGS. 11 to 13;

FIG. 15 is a view in perspective and in longitudinal section of theendoscope of FIGS. 11 to 13;

FIG. 16 is an exploded perspective view of the endoscope of FIGS. 11 to13;

FIG. 17 is an exploded perspective view of the distal end of theendoscope of FIGS. 11 to 13;

FIG. 18 is a diagrammatic fragmentary axial section view of an endoscopein a variant embodiment of the invention; and

FIG. 19 is a perspective view of the distal end of the FIG. 18endoscope.

Reference is made initially to FIG. 1, which shows a prior art device 10for searching for defects, the device comprising a rigid tubularcylindrical stick 12 for inserting via one end into an endoscopicorifice 14, e.g. made in a wall of a casing 16 of a turbine enginewithin which there is a part 18 that is to be examined, such as a rotorblade, for example.

The cylindrical stick 12 has a duct receiving means for guiding lightand for transmitting images in order to illuminate and observe the part.The cylindrical stick 12 also has a duct for spraying penetrant testmaterials, such as acetone, a penetrant dye, an emulsifier, or water.The end 20 of the stick 12 opposite from its end for inserting in theorifice 14 is connected via a circuit 22 to means 24 for feeding it withpenetrant test materials and to illumination and control means.

This type of device requires the use of a plurality of independent ductsfor passing the various penetrant test materials, thereby increasing thediameter of the endoscope and limiting its use to endoscopic orifices orpassages that are sufficiently large.

The device 26 of the invention provides a solution to that difficulty byreplacing the rigid cylindrical stick with a flexible sheath 28including an orientable examination head 62 and incorporating a duct 30in the sheath 28, which duct houses a capillary 32 slidably engagedinside the duct 30 (FIGS. 2 and 3). FIG. 3 also shows a second duct 34used for passing light-guide means and image-taking andimage-transmission means. These means are described in greater detailbelow.

The device has an endoscope handle 36 of substantially cylindrical shapewith a first end that is connected to the proximal end of the flexiblesheath 28. The second end of the handle 36 carries a bent rigid tube 38leading to the inside of the handle 36 and communicating with the duct30 housing the capillary 32.

The device 26 has means for holding the capillary 32 stationary insidethe duct 30. In a particular embodiment (FIGS. 4 and 5), these meanscomprise an endpiece 40 with a cylindrical or frustoconical skirt 42engaged and clamped on the free end of the rigid tube 38.

The endpiece 40 has a central orifice 44 enabling a capillary 32 to beinserted inside the rigid tube 38 and consequently inside the duct 30extending inside the flexible sheath 28 (FIGS. 3 and 4). The endpiece 40includes means for clamping the capillary 32 in such a manner as toprevent the capillary 32 from moving relative to the endpiece 40. By wayof example, these means are made by dimensioning the diameter of theorifice 44 so that it is slightly smaller than the outside diameter ofthe capillary 32. Thus, the capillary can be moved manually to slideinside the tube 38 and each time the operator lets go of the capillary32, the capillary is held in position. In order to enable such clamping,the endpiece 40 is made of a suitable plastics or elastomer material,such as rubber, for example.

The device of the invention also has air-blow means for blowing air fromthe distal end of the sheath. For this purpose, the endpiece 40 includesa second orifice 46 formed in its front face and leading to the insideof the rigid tube 38. This orifice 46 is connected to means 48 forfeeding air under pressure and enabling the tube 38 and the duct 30 tobe fed with a continuous stream of air 50 that leaves via the distal endof the duct 30. The exiting stream of air thus prevents the inside ofthe duct 30 becoming polluted with drops of the various penetrant testmaterials (FIG. 5) and it limits the spraying of penetrant testmaterials in the vicinity of the illumination means and the image-takingmeans formed at the distal end of the sheath.

When the pressure of the stream of air is at least 0.3 bars, it ispossible to dry the part with the air feed means, e.g. between twosuccessive applications of different penetrant test materials.

The proximal end of the capillary 32 is connected to a supply of a givenpenetrant test material. The device may then be used with a plurality ofcapillaries 32, each of which is associated with a supply of a givenpenetrant test material. Each capillary has a spray endpiece at itsdistal end enabling the penetrant test material to be sprayed in aparticular direction. The endpiece is advantageously removable and maybe replaced at will with endpieces of other types suitable forperforming spraying that is radial 52, forward 54, or backward 56 (FIG.6).

The device includes image-taking means and image-transmission means asshown in FIG. 8 a. The image-taking means comprise an image-forming lens64 transmitting the image onto a camera 66 such as a charge-coupleddevice (CCD) camera having its output connected to an analog-to-digitalconverter. The digitized image is then transferred by a cable 68 toexternal display means such as a monitor of a computer processor system.

In a particular configuration of the device of the invention, the camera66 has 500,000 pixels, each having a side lying in the range 8micrometers (μm) to 12 μm.

The device also has second image-transmission means provided inside thesheath and comprising a set of optical components (not shown)transmitting the image formed by the lens to an eyepiece 58 carried bythe proximal end of the handle.

The device also has light-guide means and illumination means extendingto the proximal end of the sheath. By way of example, these means maycomprise an optical fiber cable 70 extending from the distal end of thesheath to a connector 60 for coupling to a source of visible orultraviolet light.

In order to spray penetrant test materials in the proper directiontowards the part and in order to observe the treated zone appropriately,the device includes means for adjusting the orientation of theexamination head 62 (FIGS. 8 a and 8 b).

By way of example, these adjustment means comprise two cables that areguided inside the sheath and that have their distal ends fastened to theexamination head 62 at two diametrically opposite points 72 and 74. Theproximal portions of the cables are wound under tension in oppositedirections on a rotary control member 76 of the handle (FIG. 2). Thus,by turning the control member 76 in a given direction, the examinationhead 62 can be tilted in a plane containing the two fastener points 72and 74, and also the central axis 76 of the examination head.

It is possible to add two additional cables having their distal endsfastened to the examination head 62 at two diametrically opposite points78 and 80 that are at 90° to the two fastener points 72 and 74 of thefirst two cables. The proximal portions of these two additional cablesshould likewise be wound onto a rotary member of the handle. With suchan arrangement, it becomes possible to tilt the examination head 62 intwo orthogonal planes, one of which contains the points 72 and 74 andthe other of which contains the points 78 and 80, thereby enabling thedistal end of the sheath to be oriented in four different directions.

In order to enable the examination head 62 to be tilted, it may comprisenon-touching metal annulus 82, 84, 86 (FIG. 9). An annulus 84 isconnected to a downstream ring 82 by two blades 88 that are angularlyspaced apart by 180°, being pivotally hinged on the outer periphery ofthe downstream annulus 82 and being fastened on the annulus 84 at 180°from each other. The annulus 84 is fastened to an upstream annulus 86 bytwo blades 90 that are likewise angularly spaced apart by 180°, and thatare pivotally hinged at one end to the outer periphery of the annulus84. The second ends of the two blades 90 are fastened on an upstreamannulus 86 at 180° to each other. The blades 88 joining the annulus 84to the downstream annulus 82, and the blades 90 joining the annulus 84to the upstream annulus 86 are spaced apart at 90° from one another(FIG. 9).

Each annulus has four bridges (not shown) that are spaced apart at 90°in pairs for slidably guiding cables fastened to the distal end of theexamination head 62. In a variant embodiment of the invention, thecables for controlling the orientation of the examination head are woundunder tension on a motor-driven rotary member that may be housed in thehandle.

FIG. 10 shows an arm 92 for holding the handle of the endoscope. Thisholding arm 92 has two rods 94 and 96 that are pivotally hinged relativeto each other at 98 at a first one of their ends. A respective clamp100, 102 is pivotally hinged to the other end of each of the rods 94,96. A first clamp 100 is for clamping onto the handle of the endoscope36 and the other clamp 102 is for fastening on a portion of the turbineengine so as to enable the endoscope to be used in a static position.

In a variant embodiment of the invention (not shown), the means forfeeding air under pressure are connected to a coupling leading with therigid tube into a common cavity formed inside the handle, the proximalend of the duct leading to the inside of this cavity so as to allow thecapillary inserted from the free end of the rigid tube to pass throughand so as to allow the stream of air under pressure to flow to thedistal end of the sheath. In this configuration, the endpiece has asingle central orifice into which a capillary is inserted.

In a practical embodiment of the invention, the sheath 28 is of circularsection with a diameter lying in the range 6 mm to 10 mm, the duct 30for passing the capillary 32 has a diameter of about 1.2 mm, and thecapillary 32 has a diameter of about 0.8 mm. The flexible sheath mayhave a length of about 1.5 meters (m).

In another embodiment of the invention, the sheath may be rigid and thecapillary may be flexible or indeed rigid. Nevertheless, a rigid sheathin the form of a stick as in the prior art does not make it possible totake action in zones inside a turbine engine that are accessible onlyvia passages that are curved or not rectilinear.

Thus, using a flexible sheath with a flexible capillary makes itpossible to perform non-destructive testing of zones that are difficultto access without requiring the engine to be taken to a maintenanceworkshop, thereby reducing the time required for maintenance and thecosts of operating the engine.

Reference is made below to FIGS. 11 to 19 which show other embodimentsof the invention.

The endoscope 104 has a handle 105 with a proximal portion 106 and adistal portion 124, and a sheath forming a rigid distal inspection tube108. In FIG. 11, the tube 108 is engaged in an inspection tube 110. Thehandle 106 has a focusing ring 112 and an eyepiece 114 housed in aproximal eyecup 116 suitable for being connected to an endoscopiccamera. The endoscope 104 has a path for transmitting illumination lightcomprising a bundle of illumination fibers (not shown) extending in anillumination cable 118 secured to the handle 106. The distal portion ofthe tube 108 includes a porthole 120 at the distal end of an imageoptical path of the endoscope 104, and a window 122 behind which it ispossible to stick the previously-polished distal end of the bundle ofillumination fibers.

The endoscope has a tube 126 with a distal lateral opening 128 underwhich there are positioned the viewing window or porthole 120 and theillumination window 122 of the endoscope 104 (FIG. 11). The distal endof the tube 110 is secured to a hinge finger 130 having an internalchannel 132 leading at one end to an orifice 134 and at an opposite endinto a working channel or duct 136 housed in the tube 110. In the handle124, the working channel 136 leads into a socket 138 leading to theproximal end of the working channel 124. The working channel 124 isdesigned to enable a flexible capillary tube 32 to be slidably inserted(FIG. 15), which tube can enter via the socket 138 and leave via theorifice 134. Such a capillary tube is for spraying penetrant testmaterials onto the part to be inspected. The handle 124 also has acontrol ring 140 making it possible to adjust the angle of the hingefinger 130 manually. The handle 124 may also have a socket 142connectable to a source of compressed air, in communication with anair-blow tube 144 leading into the opening 128, parallel to the porthole120 and the illumination window 122.

In FIGS. 13, 15, and 16, the distal portion 124 of the handle 105includes a cylindrical proximal housing 146 for receiving thecylindrical distal end 148 of the proximal portion 106 of the handle 105of the endoscope 104. The housing 146 has a distal partition 150provided with an axial orifice constituting the proximal end of aninternal cylindrical tube 152 for receiving the tube 108 of theendoscope 104. Means for assembling and fastening the handle 105 in thehousing 146 may include an indexing and locking device (not shown)enabling the distal end of the tube 108 of the endoscope to be properlypositioned under the distal opening 128 of the endoscope 104.

The distal portion 124 of the handle 105 has a proximal cylindrical part154 with a proximal portion forming the cylindrical housing 146 and witha tubular distal portion 155 having a longitudinal slot 156.

The endoscope has a ring 140 for controlling the angle of the distalhinge finger 130. A cylindrical ring 158 is mounted stationary insidethe control ring 140 and has a helical slot 160 formed in its periphery.A tubular couple 162 is slidably mounted around the internal tube 152and has a radial finger 164 on its outer periphery. The shuttle 162 issecured to two longitudinal maneuvering rods 166, 168 extending insidethe tube 126 and serving to control the angle of the distal hinge finger130.

The control ring 140 and the cylindrical ring 158 are mounted around thetubular distal portion 155 of the proximal cylindrical part 154. Thetubular shuttle 162 is mounted inside the tubular distal portion 155 ofthe proximal cylindrical part 154 and the radial finger 164 passesthrough the longitudinal slot 156 of the tubular distal portion 155 ofthe proximal cylindrical part 154, and its radially outer end isreceived in the helical slot 160 of the cylindrical ring 158.

The distal portion 124 of the handle 105 also has a central part 170 anda distal part 172 which in association with the proximal cylindricalpart 154 serves to block movement in translation of the distal portion124 of the handle 105 and the cylindrical ring 158 around the tubulardistal portion 155 of the proximal cylindrical part 154, while formingtwo lateral orifices that allow sockets 138 and 142 to pass and befastened. The parts 154, 170, and 172 can thus be secured, e.g. by meansof two screws 174 a, 174 b that are engaged in orifices provided forthis purpose in the part 172 and that are screwed into the part 154.

In operation, turning the control ring 140 about the tubular distalportion 155 of the proximal cylindrical part 154 causes the radialfinger 130 to move in translation in the longitudinal slot 156, therebycausing the tubular shuttle 162 to move axially.

The distal portion of the tube 124 has a distal part 176 comprising:

-   -   a proximal tubular cylindrical portion 178 with an internal        orifice 180 provided for receiving the distal end of the        internal tube 152;    -   a middle tubular housing 182 presenting a lateral opening 128        and a distal partition 184, the housing 182 being designed to        receive the distal end of the tube 108 of the endoscope 104        inserted into the internal tube 152;    -   two distal longitudinal lugs 186, each having a transverse        orifice 188;    -   a longitudinal channel with a proximal end that receives the        blow tube 144 and a distal end leading to the housing 182;    -   a longitudinal channel having a proximal end that receives the        working channel 136 and having a distal portion leading to        between the two lugs 186; and    -   two longitudinal channels leading to between the two distal lugs        186 and slidably receiving the maneuvering rods 166 and 168.

The distal portion of the internal part 176 is associated with aninternal pulley 190 having an axial orifice 192 perpendicular to theaxis of the tube 126 and an annular groove 194 provided for guiding thecapillary tube 32 inserted into the working channel 136 via the socket138. The hinge finger 130 has two lugs 196 at its proximal end, each lugpresenting a distal transverse orifice 198 and a proximal transverseorifice 200.

The part 176, the pulley 190, and the hinge finger 130 are assembledtogether by a cylindrical pin 202 passing successively through theorifice 188 in one of the distal lugs 186 of the part 176, the orifice198 in one of the proximal lugs 196 of the finger 130, the orifice 192in the pulley 190, the orifice 198 in the other proximal lug 196, andfinally the orifice 188 in the other distal lug 186 of the part 176.

The hinge finger 130 is assembled with the maneuvering rods 166 and 168separately for each of the rods with the help of a respective transversecylindrical pin 204 inserted into the proximal orifice 200 of one of thetwo lugs 196 of the finger 130, and then in an orifice 206 provided atthe distal end of the corresponding maneuvering rod 166, 168.

In operation, the finger 130 can thus be tilted and positioned angularlybetween an axial position in which it is in alignment with the axis ofthe tube 126 (FIG. 13) and a position in which it is orientedperpendicularly to the axis of the tube 126 (FIG. 14).

A capillary tube 32 can be inserted into the working channel 136 andthen into the channel 132 while the hinge finger 130 is in its axialposition. The positioning of the distal outlet from the capillary 32 onthe part for inspection is performed by turning the control ring 140 soas to orient the finger 130 towards a direction that is perpendicular tothe axis of the tube 126 with the length of the distal portion of thecapillary tube 32 that projects beyond the finger 130 being adjustedunder visual monitoring with the help of the endoscope 104.

FIGS. 18 and 19 show a flexible video endoscope probe adapted topenetrant testing under illumination by ultra-violet (UV) light, andadapted to accessing internal zones of a turbine engine.

The video endoscope probe has a control handle with a distal end that issecured to a flexible inspection tube 208, and a proximal end that isgenerally secured to an umbilical cable (not shown) enabling the probeto be connected to operating devices, such as a light generator.

For penetrant testing, the control handle of the probe is fastened to aspecific part 210 having a distal end secured to a distal sleeve 212.The part 210 is a tubular part having an axial proximal housing withinwhich the control handle is fastened. The part 210 has an obliquelateral tubular inlet 216 with an outside end that presents internaltapping 214.

The sleeve 212 may be made of a flexible material, and it surrounds theproximal end of the inspection tube 208. The inspection tube 208includes a flexible distal angulation 218 and a distal examination head220 housing an optoelectronic device having illumination means andimage-taking means analogous to those described with reference to FIGS.8 a and 8 b. A nut ring 222 is fastened on an outside thread 224 at thedistal axial end of the part 210 in order to secure the part 210 inleaktight manner with the sleeve 212.

The part 210 has an axial tubular channel 226 housing the followingconnections:

-   -   a bundle of illumination fibers 228;    -   four flexible sheaths 230; and    -   a multiconductor electric cable 232.

The bundle of illumination fibers 228 connects an axial illuminationwindow 234 situated on a distal face of the distal head 220 withoutdiscontinuity to the proximal end of the umbilical cable of the videoendoscope probe. The proximal end of the umbilical cable may beconnected to an illumination generator suitable for delivering equallywell white light or UV light.

The four sheaths 230 are designed to guide four flexible control cableswhose distal ends are secured to the distal angulation 218 and whoseproximal ends are actuated by a manual or motor-drive control member,which may be housed in the control handle. The control cables and thecontrol member may be similar to those described with reference to FIGS.8 b and 9.

The multiconductor electric cable 232 connects the image sensor housedin the distal head 220 to a video processor that may be housed in thecontrol handle. The main functions of the video processor are tosynchronize the distal image sensor and to transform the electric signaldelivered by the sensor into a standardized video signal. The imagesensor is associated with a lens 235 forming a viewing window that islikewise located in the distal face of the head 220.

The oblique tubular inlet 216 of the part 210 is designed to receive theproximal portion 236 of a working channel or duct, which proximalportion is fastened in the oblique tubular inlet 216, e.g. by adhesive.The proximal portion 236 may be made of a rigid material, e.g. a metal.The distal end of the proximal portion 236 of the working channel issecured (with the help of a releasable device for maintenance purposesthat is not shown) to the proximal end of a flexible proximal portion238 of the working channel as received in the inspection tube 208. Thedistal end 238 of the proximal portion of the working channel leads toan orifice 241 formed in the distal face of the distal head orexamination head 220 (FIG. 5A).

The distal end of an intermediate tubular part 240 is screwed (oradhesively bonded) in the oblique tubular inlet 216 of the part 210 bymeans of a distal outside thread.

A coupling part 246 including a lateral inlet 242 and a proximal axialinlet may be associated in leaktight manner with the part 240 by meansof a ring 244 screwed onto the periphery of the intermediate part 240and held axially against an annular rim of the coupling part. A sealing0-ring is clamped at the interface between the coupling part 242 and theintermediate tubular part 240. The proximal axial inlet of the couplingpart 246 presents a diameter that is slightly greater than the diameterof a flexible capillary 32 suitable for being inserted therein. Theproximal axial inlet of the part 246 may be fitted with a removablesealing cap 248 made of a flexible material and presenting an axialorifice into which the operator can insert a capillary tube 32 that iscapable of sliding in the working channel 236, 238 until its distalportion emerges from the orifice 241 in the distal face of the distalhead 220. The lateral inlet 242 of the part 246 is connected to meansfor feeding air under pressure. Under such conditions, the air injectedvia the inlet 242 flows in the annular space between the outside surfaceof the capillary tube 32 and the inside surface of the working channel236, 238 until it exits via the orifice 241 in the distal head 220. Inthis way, the air as injected in this way via the inlet 242 can preventthe penetrant test materials sprayed by the remote outlet of thecapillary tube 32 from becoming deposited on the viewing window 235 andthe illumination window 234 on the distal face of the head 220, therebyserving to clean these windows. The air injected into the workingchannel also avoids the working channel being polluted by drops of thepenetrant test material.

The ability to disconnect the coupling device 246 directly constitutesan important advantage in terms of maintenance, insofar as it makes iteasier to clean the working channel 236, 238 periodically.

In another embodiment, the illumination device of the video endoscopeprobe may comprise at least two light-emitting diodes (LEDs), oneemitting white light and the other emitting UV light, these two LEDsbeing installed in the distal end of the probe.

In embodiments that include a bundle of illumination fibers, the bundleof illumination fibers may be replaced by a liquid light guide suitablefor transmitting UV light and white light, or it may be associated withsuch a liquid light guide that may be removable.

It can clearly be seen by the person skilled in the art that the presentinvention may be subjected to a wide variety of embodiments andapplications. In particular, the above-described video endoscope probemay include an air-blow tube that is distinct from the working channeland that leads to the distal head 220 of the probe so as to deliver aironto the illumination and viewing windows.

The endoscope of the invention may be used with inspection tubes thatare flexible or rigid. In an endoscope or a video endoscope having aflexible inspection tube fitted with a distal angulation, the viewingand illumination windows may be lateral or axial. When these windows areaxial, the tube 126 has an opening enabling these windows to be orientedlaterally with the help of the angulation. When the windows are lateral,the angulation may be omitted.

In the various embodiments of the invention as described above, theillumination fibers are made of a material suitable for transmittingboth visible light and UV light, e.g. they are made of quartz or of apolymer that is suitable for transmitting both white light and UV light.

By blowing air over the illumination means and the image-taking means,there is no need at any time to remove the inspection tube from theendoscopic inspection orifice, in particular during or after sprayingpenetrant test materials onto the part for inspection, and the tube canremain in place until the end of visually inspecting the part underillumination with UV light, thereby reducing the time needed forendoscopic inspection operations.

Injecting air into the working channel 236, 238 while injectingpenetrant test materials, in combination with the fact that thecapillary tube immerses from the distal end of the working channel,contributes to greatly reducing the amount of pollution both in theworking channel and on the examination head.

It may be preferable to avoid mixing penetrant test materials. Undersuch circumstances, a different capillary tube 32 may be used forinjecting each penetrant test material. The capillary tubes that areused may thus be single-use tubes.

1-17. (canceled)
 18. A device for searching for defects on parts thatare masked and accessible via a passage that is not rectilinear inside aturbine engine, or on an airplane turboprop or turbojet, the devicecomprising: a tubular sheath; light-guide means for guiding light;image-transmission means for transmitting images housed in the sheath toilluminate and observe a part for inspection; an examination head at adistal end of the sheath, the head including illumination means andimage-taking means connected to the light-guide means and to theimage-transmission means housed in the sheath; means for spraying asuccession of penetrant test materials on the part for inspection,comprising a capillary slidably guided inside a duct housed in thesheath; and means for adjusting an orientation of the examination headat the distal end of the sheath.
 19. A device according to claim 18,further comprising air-blow means for blowing air on the illuminationmeans and on the image-taking means located at the distal end of thesheath.
 20. A device according to clam 19, wherein the air-blow meanscomprises means for feeding air under pressure that are connected to ablow tube leading at its distal end to a vicinity of the illuminationmeans and the image-taking means.
 21. A device according to claim 20,wherein the means for feeding air under pressure is connected to aproximal end of the duct for passing the capillary to feed the duct witha continuous stream of air that leaves via its distal end.
 22. A deviceaccording to claim 18, wherein a proximal end of the sheath is connectedto a handle for fastening to the engine, and the duct housing thecapillary is extended inside the handle and is connected to a rigid tubecarried by the handle and serving to insert the capillary into an insideof the duct.
 23. A device according to claim 22, further comprisingholder means for preventing the capillary from sliding inside the duct.24. A device according to claim 23, wherein the holder means comprisesan endpiece including means for clamping onto the capillary andconfigured to be engaged and held on a free end of the rigid tube.
 25. Adevice according to claim 24, wherein the endpiece includes a passageleading to an inside of the tube and forming an inlet for connection toa means for feeding air under pressure.
 26. A device according to claim22, wherein the orientation adjustment means comprises a control memberfor controlling angular orientation of the examination head, whichmember is rotatably mounted on the handle and is connected totransmission means for transmitting the orientation control to theexamination head, the transmission means being housed in the sheath. 27.A device according to claim 25, wherein the means for adjusting theorientation of the examination head comprises at least two cables guidedinside the sheath and fastened at their distal ends to the examinationhead at two diametrically opposite points, and wound under tension attheir proximal portions in opposite directions on a rotary controlmember situated on the handle.
 28. A device according to claim 26,wherein the means for transmitting the orientation control comprises atleast one rod extending inside the sheath and connected at its distalend to a mechanism for converting rotary movement of the ring intomovement in translation of the rod, the rod being connected by itsdistal end to a finger that is pivotally hinged to the distal end of thesheath about an axis that is perpendicular to the sheath.
 29. A deviceaccording to claim 28, wherein the distal finger includes an axialchannel for passing the capillary and is hinged to pivot between aposition in which it is in alignment with an axis of the sheath and aposition in which it is oriented perpendicularly to the axis of thesheath.
 30. A device according to claim 18, wherein the tubular sheathis flexible, and the capillary is flexible.
 31. A device according toclaim 18, wherein the distal end of the sheath includes a spray endpieceat its distal end.
 32. A device according to claim 31, wherein the sprayendpiece at the distal end of the capillary is removable and can beselected from a set of spray endpieces for spraying radially, forwards,or backwards.
 33. A device according to claim 18, wherein the sheath isof circular section with a diameter lying in a range of 6 mm to 10 mm,and the duct for passing the capillary has a diameter of about 1.2 mm,the capillary having a diameter of about 0.8 mm.
 34. A method ofnon-destructive penetrant testing of a part that is masked, by using adevice according to claim 18, the method comprising: inserting andguiding the examination head inside a three-dimensional structure to aposition for examining the part for inspection; with the examinationhead placed facing the part for inspection, feeding the proximal end ofthe capillary with a first penetrant test material and applying thefirst material via the distal end of the capillary to the part forinspection; slidably withdrawing the capillary from the duct in which itis housed; and slidably inserting a second capillary into the duct andbringing its distal end into a vicinity of the part for inspection, andthen feeding the proximal end of the second capillary with a secondpenetrant test material and applying the second material via the distalend to the part for inspection.